1. Field of the Invention
The present invention generally relates to fixed frame communications and, more particularly, to packaging of data for fixed frame communications.
2. Background of the Invention
Push-to-talk (PTT) communications were originally implemented using half-duplex communication systems. However, with the proliferation of cellular communication systems in recent years, PTT communications now are available over a variety of packet based digital communication systems. Examples of packet based digital communication systems include those based on General Packet Radio Services (GPRS), the Universal Mobile Telecommunications System (UTMS), Code Division Multiple Access (CDMA), etc.
Oftentimes, a half-rate enhanced variable rate codec (half-rate EVRC) is used to encode PTT data into frames, which are then packetized for communication over a packet based communication system. For example, when the PTT data is packetized in accordance with the 1x Evolution Data Optimized revision A (DOrA), for example, each data packet contains six (6) half-rate EVRC frames, which are each eighty (80) bits in length. Thus, the total PTT data length of 480 bits. An additional 344 bits is usually allocated for overhead (e.g. headers, footers, etc.), thus providing a total length of 824 bits.
Packet sizes in digital communications typically are binary based. Accordingly, conventional packet sizes are generally limited to values determined by raising the base value of two (2) to a particular power, or exponent. For instance, the C.S0024-A standard proposed for use by the Third Generation Partnership Project 2 (3GPP2) defines data packet sizes that may be used for transmitting a reverse traffic channel packet. A reverse traffic channel is used by a communication device to transmit user-specific traffic or signaling information via an access network. The data packet sizes that are defined in C.S0024-A are 28 (i.e. 256) bits, 29 (i.e. 512) bits, 210 (i.e. 1024) bits, 211 (i.e. 2048) bits, and 212 (i.e. 4096) bits.
In the present example, the total bit length of the DOrA PTT data, which is 824 bits, is too long to entirely fit into a conventional packet that is less than 1024 bits in length. Accordingly, when communicating DOrA PTT data, a 1024 bit packet is typically used, thus leaving two hundred (200) unused bits in each data packet. These unused bits are usually set to a particular value (e.g. zero), and thus represent wasted bandwidth.